Electric switch



Dec. 27, 1955 E. J. DE NOYERS ELECTRIC SWITCH Filed Oct. 15, 1955Inventor. Emil JDeN eF's, 10 3 l-lis Attorngs.

United States P O ELECTRIC SWITCH Emil J. De Noyers, Pittsfield, Mass.,assignor to General Electric Company, a corporation of New YorkApplication October 15, 1953, Serial No. 386,157

3 Claims. (Cl. 200-16) This invention relates to electric switches andmore particularly to improvements in switches of the type in which acommon contact makes selective engagement with a plurality of relativelyfixed contacts.

A switch of the type used in connection with the present invention isdisclosed and claimed in Minneci Patent 2,418,363, assigned to the sameassignee as the present application. The Minneci patent was directed toan in-linetype switch in which solid insulation was introduced betweenthe movable contact assembly and all of the fixed contacts, except theparticular fixed contact with which the movable contact was inengagement and in which the creepage distance along the solid insulationwas automatically made so that it was substantially proportional to thevoltage difference between any fixed contact and the movable contactassembly. The Minneci structure comprised a plurality of fixed contactssupported in a straight line and adapted to be connected to points in anelectrical winding having progressively increasing voltage, a movablecontact assembly for successively engaging the fixed contacts, themovable contact assembly including electrical conducting means extendinggenerally parallel to the line of the relatively fixed contacts andspaced therefrom, a pair of concentric insulating cylinders havingoppositely extending oblique slots and being free to rotate, and amovable contact member extending through the slots and attached to theconducting means extending generally parallel to the aligned fixedcontacts.

The Minneci type switch is useful as a tap changer for multitap windingssuch as the windings of a reactor or a transformer. In fabricating aswitch of this type some difiiculty has been experienced in mounting themovable contact assembly inside the rotatable cylinders with thecontacting portion extending through the diamond-shaped aperture formedat the crossover point of the oblique slides. Therefore, it is an objectof the present invention to provide a movable contact which willsimplify assembling operations on a Minneci type switch.

It is another object of the invention to provide a Minneci switch havinga movable contact which can be readily positioned on the interior of asmall-sized rotatable cylinder.

Other objects will be apparent from the specification and drawingwherein Fig. 1 is a front elevation partly in section illustrating amovable contact in accordance with this invention mounted in place on aMinneci switch; Fig. 2 is a view of the rotatable cylinders of theswitch of Pig. 1 showing the movable contact extending through theaperture formed at the crossover point of the oblique slots in thecylinder walls; Fig. 3 is an enlargement of the movable contact portionof the switch illustrated in Fig. 1; Fig. 4 is a view taken along theline 44 of Pig. 3; Fig. 5 is a view similar to Fig. 4 showing thecontact fingers in the retracted position they would occupy prior toassembly; and Fig. 6 is a view taken along the line 66 of Fig. 4.

Briefly stated, in accordance with one of its aspects, this invention isdirected toward an extendable contact assembly comprising an elongatedmember having a pair of oppositely spaced grooves, means for mountingthe member on a threaded shaft, a centrally slotted contact fingerhaving a contact in position in each of the grooves, the contact fingersbeing of a length about equal to the elongated member and being movablethrough the grooves of the elongated member, the contact finger slotsbeing in register and having a depression adapted to seat a washer atthe end of each slot opposite the contact end of the finger, a pinmounted on the elongated member and extending transversely outward fromthe contact fingers through the slots, a washer on each end of the pinin engagement with a contact finger, and a spiral compression springmounted on each end of the pin, each spring bearing against itsassociated washer to impart clamping action to the contact fingers andseat the washer in their respective depressions when the contact fingersare in an extended position.

The switch illustrated in Fig. 1 comprises a pair of end plates 10 and11 which are held apart by members 12 and 13. The member 12 ispreferably of insulation which may be a cylinder of synthetic resinbonded laminated insulating material and the member 13 is preferablymade of metal so as to be an electrical conductor extending through thebottom plate 11 so as to form the common terminal of the switch.Extending transversely through the insulating cylinder 12 are aplurality of insulating members 14 which may also be of synthetic resinbonded laminated insulating material and which carry on their left-handends metal contacts 15 which are connected respectively to cables 16which may lead to different taps on a winding (not shown).

For making selective contact with the fixed contacts 15 there is amovable contact assembly 17 threaded directly on a screw shaft 18 or ona traveling screw (not shown) mounted upon the screw shaft 18. Thethreaded screw shaft 18 is rotated by a wheel 19 mounted outside the endplate 10. The wheel 19 may be a gear rotated by another gear (notshown). The movable contact assembly 17 makes sliding engagement withthe conductor member 13. Other parts of the movable contact assembly 17will be described in more detail hereinafter.

For insulating the conducting parts of the movable contact assembly 17from the fixed contacts 15 the parts are surrounded by a pair ofconcentric insulating cylinders 21 and 22 which may also be made ofsynthetic resin bonded laminated insulating material. These are providedwith oblique slots 23 and 24, respectively, extending in oppositedirections these slots being just wide enough to allow the contactfingers of the movable switch assembly 17 to pass therethrough.

The entire switch assembly may be submerged in insulating fluid, such asmineral oil or askarel, which often fills or substantially fills thetank of a high voltage transformer. If so, it will be understood thatthe liquid will fill the cylinders 21 and 22.

Referring particularly to Figs. 3-6, the structure of the movablecontact assembly 17 will now be described. An elongated body portion 26adapted to engage the condoctor 13 and to be moved in a lateraldirection by the threaded shaft 18 has a pair of oppositely disposedgrooves in which are positioned a pair of contact fingers 27 and 28. Thecontact fingers 27 and 28 have an extendable contact end adapted to makeclamping engagement with the stationary contacts 15. The contact fingers27 and 28 are maintained in sliding engagement with the grooves in thebody portion 26 by means of a pin 29 mounted so as to pass through thebody section 26 and also through longitudinal slots centrally disposedin the contact fingers 27 and 28. The exterior end of the finger slotsmost removed from the contact end has a depression adapted to seat aWasher. Mounted upon the pin 29 are a spiral 3 biasing spring 31positionedbetween a retaining washer 32 fixedly positioned by a cotterpin 33 and movable washer 34 bearing against the contact finger 27 toexert clamping ressure thereon. A similar assembly for the contactfinger 23 comprises the spiral spring '35, washer 36, cotter pin 37 andwasher 38.

Prior to assembly on the switch illustrated in Fig. 1 the movablecontact assembly 17 is in the retracted form illustrated in Fig. 5. Inthis form it can readily be inserted inside the cylinder 22 andpositioned in line with the diamond-shaped opening at the crossoverpoint of the oblique slots in the cylinders. The contact fingers 27 and28 are then extended through the opening until the washers 34 and 38engage and are seated upon the depressions at the end of the contactfinger slots. This locks the contact fingers in extended position andthe mounting of the movable contact assembly 17 on the switch iscomplete.

With the contact assembly 17 in position on the switch illustrated inFig. 1 it will be seen that the distance between the slots at the bottomof the cylinders is a maximum, and, as the voltage of the metallic partsof the movable contact assembly 17 corresponds to the voltage of the topfixed contact 15, the voltage between the movable contact assembly 17and the lowermost fixed contact 15 will be a maximum. The creepage pathbetween the lowermost stationary contact 15 and the metallic elements ofthe contact assembly 17 which extends through the annular space betweenthe cylinders 21 and 22, is then very long in comparison with thestraight line distance between these metallic elements. The horizontaldistance between the slots gets less and less as the vertical distanceto the movable contact is decreased but as the voltage differencebetween the movable contact and any fixed contact is proportional to thevertical distance between them, the effective insulation and creepagedistance is proportional to the voltage stress.

While there has been shown and described a particular embodiment of thisinvention it will be understood by those skilled in the art that variouschanges and modifications can be made therein without departing from theinvention; therefore, it is aimed in the appended claims to cover allsuch changes and modifications as fall within the true spirit and scopeof the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A switch comprising, in combination, a plurality of relatively fixedcontacts insulatingly supported in a straight line and adapted to beconnected respectively to points in an electrical winding havingprogressively increasing voltage, a movable contact assembly forsuccessively engaging said fixed contacts, said movable contact assemblyincluding electrical conducting means extending generally parallel tothe line of said relatively fixed contacts and spaced therefrom, a pairof concentric insulating cylinders surrounding said last-mentioned meansand having oppositely extending oblique slots, said cylinders being freeto rotate, and a contact member extending through said slots, and havingaxial movement through said cylinders, said contact member having anelongated body portion in engagement with said conducting means whichextends generally parallel to said aligned fixed con tacts, a pair ofoppositely disposed longitudinal grooves in said body portion, aclamping contact finger positioned in each groove and havinglongitudinal movement with respect thereto, each of said fingers havinga contacting end and centrally positioned longitudinal slot, said slotsbeing in register, the end of each slot opposite the con tacting endhaving a circular impression adapted to seat a washer, a pin extendingthrough the slots, a pair of washers mounted on said pin and inengagement with the contact fingers, and a pair of spiral biasingsprings mounted on said pin and bearing against said washers wherebyclamping action is exerted on said contact fingers and they are lockedin extended position when said Washers are seated in said circularimpressions.

2. A clamping contact assembly adapted for assembling in a narrow spacecomprising an elongated body section, means for mounting said bodysection upon a conductor, a pair of oppositely disposed longitudinalgrooves in said body section, a clamping contact finger having a contactend in each groove, said fingers being movable along said grooves, alongitudinal slot centrally positioned in each contact finger, saidslots being in register, a circular depression adapted to seat a washerat the end of each longitudinal slot opposite the contact end of saidfinger, a pin extending through said slots and transversely outward onboth sides of said body section, a washer mounted on said pin from eachend in engagement with a finger, and a biasing spring mounted on eachend of said pin, said biasing springs exerting pressure against saidwashers whereby said fingers are subjected to clamping action and areheld in extended position with respect to said body section when saidWashers become seated in their respective depressions.

3. An extendable contact assembly comprising an elongated member havinga pair of oppositely spaced grooves, means for mounting said member on ascrew shaft, a centrally slotted contact finger having a contact endpositioned in each of said grooves, said contact fingers being of alength about equal to said elongated member and being movable throughsaid grooves, said slots being in register, a depression adapted to seata washer at the end of each slot opposite the contact end of saidfinger, a pin mounted on said elongated member and extendingtransversely outward on both sides through said slots, a washer at eachend of said pin in engagement with a contact finger, and a spiralcompression spring mounted on each end of said pin, each spring bearingagainst its associated washer to impart clamping action to said fingersand seat said washers in their respective depressions when said fingersare in an extended position.

References Cited'in the file of this patent UNITED STATES PATENTS

